Development of non-destructive methods for the determination of airborne pollutants in pine needles: identification of trace constituents in radiata pine epicuticular wax

Abstract

In an attempt to develop non-destructive work-up procedures for monitoring lipophilic pollutants in the air by analysis of pine needle epicuticular wax, a project was undertaken to identify substances that interfere with the normal gas-chromatographic quantitations. Epicuticular wax was extracted from needles of radiata pine and processed to remove the bulk estolides and resin and fatty acids. Fractionation of the residue on a silica gel column gave three fractions, representing less than 0.2% of the wax. The fractions contained a mixture of natural products and anthropogenic chemicals. Among the natural products were sesquiterpenes, comprising mainly amorphene, cadinenes, germacrene and cadalene; bisnor-, nor- and diterpene hydrocarbons; methyl esters of resin acids; and 9,10-secodehydroabietanes of unknown ring-A structure. Some of these compounds have not been reported from pine needle epicuticular wax previously. Anthropogenic chemicals identified include polycyclic aromatic hydrocarbons. The organochlorine compounds of environmental importance were hexachloro-cyclohexanes (including lindane), hexachlorobenzene, pentachloroanisole, chlordanes, dieldrin, p,p′-DDE, p,p′-DDT, and penta-, hexa- and heptachlorobiphenyls. The organochlorine compounds were present at concentration orders of magnitude lower than the interfering compounds, and therefore had to be identified using gas chromatography-mass spectrometry methods. By identifying the interfering compounds, non-destructive work-up procedures could be developed in order to retain the integrity of all of the anthropogenic compounds contributing to environmental pollution.